Question

evaluate : `int xcosxdx`

Answer 1

`"Let " I=int x cosx dx`

integrating by parts

`I=x int cosx dx-int[d/dx(x)int cosxdx]dx`

`=xsinx-int(sinx)dx+c`

`=xsinx-(-cosx)+c`

`=xsinx+cosx+c`